1. Field of the Invention
This invention relates generally to manually operated, semiautomatic and automatic rifles and, in particular, to upper receiver assemblies for AR-15 rifles, especially those that can be converted for accurate firing of cartridges of at least two different calibers.
2. Background Art
Increased flexibility of use of a gun may be achieved by providing a system that permits the firing of cartridges of dissimilar caliber. For instance, military, police and civilian marksmen can thereby train with a firearm on indoor and short distance ranges and with relatively inexpensive rim fire cartridges, specialty training cartridges or pistol-type cartridges.
In the case of handguns, U.S. Pat. No. 6,493,979 to Katzmaier disclosed a system that included a first barrel removably mounted to a handgun, with the first barrel including a first cartridge chamber sized to permit placement of the first cartridge into the first barrel in firing position. The first cartridge chamber was sized to prevent placement of the second cartridge into the first cartridge chamber in the firing position. A second barrel was provided, which was interchangeable with the first barrel and which was also removably mounted to the handgun. The second barrel included a second cartridge chamber sized to permit placement of the second cartridge into the second barrel in the firing position, and the second cartridge chamber was sized to prevent placement of the first cartridge into the second cartridge chamber in the firing position.
U.S. Pat. No. 4,404,765 to Reudelsterz et al. disclosed a small caliber conversion assembly and small caliber cartridge for a large caliber gun, such as a field howitzer or a tank-borne gun, that utilized an adapter that was insertable into a large cartridge chamber of the gun. The adapter carried a small caliber cartridge and firing means for the small caliber cartridge that was responsive to the large caliber gun firing mechanism.
United States patent application Publication No. US 2004/0244258 of O'Dwyer et al. disclosed a barrel assembly for insertion into a parent barrel of a rifle that permitted the conversion of the gun barrel to a smaller caliber barrel using a barrel insert. The barrel assembly had a plurality of projectiles axially disposed within at least one barrel of the barrel assembly and associated with discrete selectively ignitable propellant charges for propelling the projectiles from said at least one barrel, wherein said barrel assembly included a parent barrel engaging means. In one embodiment, the barrel assembly comprised a single barrel. In another embodiment, the barrel assembly included a cluster of barrels aligned in a closed packed array for insertion into the parent barrel.
There remains a need, however, for a system that is capable of converting a manually operated, semiautomatic or automatic rifle for accurate firing of cartridges of at least two different calibers; and, there remains in particular a need for such a system that is capable of such a conversion of an AR-15 rifle. AR-15 is a trademark of the Colt Manufacturing Company of Hartford, Conn., and designates a civilian version of a military M-16 assault rifle.